A fuel cell, like an ordinary battery, provides direct current electricity from two electrochemical reactions. These reactions occur at electrodes to which reactants are fed. For example, in a direct methanol fuel cell (DMFC), a negative electrode (i.e., anode) is maintained by supplying a fuel such as methanol, whereas a positive electrode (i.e., cathode) is maintained by supplying oxygen or air. When providing a current, methanol is electrochemically oxidized at an anode electro-catalyst to produce electrons, which travel through an external circuit to a cathode electro-catalyst where they are consumed together with oxygen in a reduction reaction. A circuit is maintained within the DMFC by the conduction of protons in an electrolyte.
A fuel cell stack typically includes a series of individual fuel cells. Each cell includes a pair of anode and cathode. A voltage across each cell is determined by the type of electrochemical reaction occurring in the cell. For example, for a typical DMFC single cell, the voltage can vary from 0 V to 0.9 V, depending on a current being generated. The current being generated in the cell depends on the operating condition and design of the cell, such as electrocatalyst composition/distribution and active surface area of a membrane electrode assembly (MEA), characteristics of a gas diffusion layer (GDL), flow field design of an anode and cathode bi-polar plates, cell temperature, reactant concentration, reactant flow and pressure distribution, reaction by-product removal, and so forth. The reaction area of a cell, number of cells in series, and the type of electrochemical reaction in the fuel cell stack determine a current and hence a power supplied by the fuel cell stack. For example, typical power for a DMFC stack can range from a few watts to several kilowatts. A fuel cell system typically integrates a fuel cell stack with different subsystems for the management of water, fuel, air, humidification, and thermal condition. These subsystems are sometimes collectively referred to as balance of the plant (BOP).
Precise alignment is an important aspect in a fuel cell stack assembly process. Any misalignment can lead to fluid or gas leaks that can impact performance or cause damage to a fuel cell stack. Many components that make up the fuel cell stack are assembled in series, which can increase the complexity of the assembly process. These components are typically positioned in one assembly and aligned to a single reference point within thousandths of an inch. This alignment was previously performed by pushing the components against a straight edge or sometimes by eye estimation, where accuracy and efficiency were difficult to achieve. As a result, it can sometimes take up to 8 to 10 hours to complete the assembly process. It is against this background that a need arose to develop the assembly jig and related methods described herein.
Therefore, there is a need for an apparatus and method for fuel cell stacking.